Radiation dose optimization for photon-counting CT coronary artery calcium scoring for different patient sizes: a dynamic phantom study

Abstract

Purpose To systematically assess the radiation dose reduction potential of coronary artery calcium (CAC) assessments with photon-counting computed tomography (PCCT) by changing the tube potential for different patient sizes with a dynamic phantom. Methods A hollow artery, containing three calcifications of different densities, was translated at velocities corresponding to 0, < 60, 60–75, and > 75 beats per minute within an anthropomorphic phantom. Extension rings were used to simulate average- and large -sized patients. PCCT scans were made with the reference clinical protocol (tube potential of 120 kilovolt (kV)), and with 70, 90, Sn100, Sn140, and 140 kV at identical image quality levels. All acquisitions were reconstructed at a virtual monoenergetic energy level of 70 keV. For each calcification, Agatston scores and contrast-to-noise ratios (CNR) were determined, and compared to the reference with Wilcoxon signed-rank tests, with p < 0.05 indicating significant differences. Results A decrease in radiation dose (22%) was achieved at Sn100 kV for the average-sized phantom. For the large phantom, Sn100 and Sn140 kV resulted in a decrease in radiation doses of 19% and 3%, respectively. Irrespective of CAC density, Sn100 and 140 kVp did not result in significantly different CNR. Only at Sn100 kV were there no significant differences in Agatston scores for all CAC densities, heart rates, and phantom sizes. Conclusion PCCT at tube voltage of 100 kV with added tin filtration and reconstructed at 70 keV enables a ≥ 19% dose reduction compared to 120 kV, independent of phantom size, CAC density, and heart rate. Key Points • Photon-counting CT allows for reduced radiation dose acquisitions (up to 19%) for coronary calcium assessment by reducing tube voltage while reconstructing at a normal monoE level of 70 keV. • Tube voltage reduction is possible for medium and large patient sizes, without affecting the Agatston score outcome.

Ex vivo coronary calcium volume quantification using a high-spatial-resolution clinical photon-counting-detector computed tomography

“…Recent studies by Eberhard et al, 23 van der Werf et al, 25 Wolf et al, 47 and Dobrolinska et al 48 similarly investigated CAC imaging on the NAEOTOM Alpha PCD-CT with an emphasis on assessing calcium scoring. In those studies, however, the standard detector collimation of 144 × 0.4 mm was used.…”

Thin slice photon‐counting CT coronary angiography compared to conventional CT: Objective image quality and clinical radiation dose assessment

“…Photon-counting CT (PCCT) is a new generation of computed tomography (CT) technology that is increasingly being investigated in coronary CT angiography (CCTA) thanks to its advantages over conventional energy-integrating detector CT (EID-CT). [1][2][3][4][5][6][7][8][9][10][11] PCCT scanners contain photon-counting detectors (PCD's), which can directly convert incoming photons to an electrical signal proportional to the photon's energy and register such events for individual photons. One of the advantages over conventional CT, is the high spatial resolution of PCCT.…”